The present invention relates generally to a dust boot for a ball and socket joint. More particularly, the invention relates to a dust cover that has an elongated sleeved body portion and a hinged upper portion that permits the joint to move through its range of motion while reducing wear of the dust boot.
Ball and socket joints are used in a variety of applications, including rack and pinion inner tie rod socket assemblies, steering knuckles, drag links, and connecting rod assemblies. Ball and socket joints typically include a generally cylindrical socket adapted to receive a bearing together with a head of a ball stud. Ball joints further typically include a dust cover for sealing the opening between the socket and the ball stud to keep contaminants, such as debris and foreign fluid, out of the ball and socket joint to prolong the wear life of the joint.
Known ball and socket joints include a machined groove around the outside of the socket. The side wall of the dust cover is externally attached to the housing by means of a spring wire clip that cooperates with the external groove. However, this method of attachment of the dust cover has disadvantages. First, the groove must be machined into the housing to precise tolerances. The machining step increases production costs. Further, grooves that do not achieve the desired tolerance range result in wasted material. Additionally, a spring wire clip must be incorporated into the seal.
However, the incorporation of a spring wire clip increases handling and assembly costs. Spring wire clips also may become distorted and/or incorrectly installed around the dust cover during assembly which could compromise sealing effectiveness and increase the potential for dust cover damage. In addition, the spring wire clip may become dislodged during operation of the joint such that the dust cover may uncover the joint, exposing the internal components of the joint to contaminants.
Another known ball and socket joint includes a press-on type dust cover. Press-on dust covers have an integral flange containing a flat spring steel insert having biting edges. To attach the dust cover to the socket, the integral flange is pressed down over the hollow-milled socket until properly positioned. The biting edges secure the dust cover against the side of the hollow-milled area of the socket housing. Press-on dust covers are undesirable as the expense to produce the dust covers is increased because of the costs associated with the integral spring steel insert. Further, there is an increased potential for damage to the dust cover when pressing it onto the socket housing due to overpressing.
Other known ball and socket joints include a xe2x80x9cslidingxe2x80x9d type dust cover. Sliding type dust covers have a short side wall that extends around the edge of the socket housing near the housing opening and slide along the ball stud as the stud oscillates up and down. To insure against bunching up or bowing (xe2x80x9cwrapping upxe2x80x9d) as the dust cover is continually forced to slide up and down to follow the motion of the ball stud, sliding dust covers include thick, short side walls having a typical thickness in the range of 0.090xe2x80x3-0.120xe2x80x3 (2.286 mm-3.048 mm). In some instances, the sliding dust covers also incorporate surface ribs to reduce the flexibility of the side wall for increased tracking of the dust cover with the ball stud. However, sliding dust covers are disadvantageous in applications where the joint has considerable range of stud motion as the short, thick side walls used in sliding dust covers may become dislodged from the socket during operation, thereby exposing the internal components of the joint to corrosive effects of the environment.
The present invention is relates to an improved dust cover for use with a conventional ball and socket joint for keeping debris and foreign fluid out of the joint. The ball and socket joint includes a joint housing, inner and outer bearings, and a ball stud. In accordance with the invention, the dust cover is constructed of a flexible, elastomeric material having a generally M-shaped cross-section. The dust cover includes an elongated sleeved body portion that defines a first diameter and a hinged upper portion that defines a second diameter.
The sleeved body portion has a generally cylindrical shape that corresponds to shape of the socket housing and a diameter that is slightly smaller than the diameter of the housing. The thickness of the dust boot is generally thinner than known dust covers, preferably between 0.040xe2x80x3-0.060xe2x80x3 (1.016 mm-1.524 mm) to provide greater flexibility of the dust cover flexibility during ball stud articulation.
After assembly of the ball joint, the sleeved body portion of the dust cover is stretched over the joint housing such that the sleeved body section tightly encircles and grips the side wall of the joint housing substantially below the socket opening. Preferably, a distal end of the sleeved body portion is positioned at a bottom section of the joint housing, spaced away from the joint housing opening. Because the first diameter of the sleeved body portion is slightly smaller than the housing diameter, once the sleeved body portion is stretched over the joint housing, a section of the sleeved body portion is frictionally retained on the housing without requiring any additional fasteners. Further, the elongated nature of the body portion of the dust cover provides additional surface contact between the dust cover and the housing as compared to known dust boots, such that the body portion does not slide during ball joint operation. Thus, accidental dislodgment of the body portion from the housing is substantially eliminated, preventing the ball joint components from being exposed to debris, water and other contaminants.
The hinged portion of the dust cover includes a sealing lip, upper hinges, and a lower hinge. The sealing lip defines the second diameter of the dust cover. The second diameter is substantially smaller than the first diameter of the sleeved body portion and is sized such that an interior surface tightly encircles a shank of the ball stud. The outer surface of the sealing lip has a channel-shaped groove formed therein. The channel-shaped groove receives a fastening ring to securely seal the sealing lip against the ball stud.
The sealing lip and a transition end of the sleeved body portion are connected together by the upper and lower hinges. The hinges serve to provide additional surface material such that the hinged portion of the dust cover has increased flexibility, thereby prolonging wear life of the dust cover. In the preferred embodiment, the hinged portion includes a first upper hinge positioned adjacent to and extending outwardly and downwardly from the sealing lip. A second upper hinge positioned adjacent to and extending inwardly and downwardly from a top portion of the sleeved body portion. The lower hinge is positioned between the first and second minor hinges, forming an external groove on an outer top surface of the dust cover between the first and second upper hinges and providing internal grease nest areas on either side of the lower hinge. The first upper hinge is offset so as to be slightly higher than the second upper hinge. Due to the offset hinges, planar and torsional twisting of the dust cover are distributed over the hinges. Thus, the dust cover may simultaneously follow the articulation and rotation of the ball stud with only minor and inconsequential wrapping up of the dust cover material.